Dynamical studies of fully deuterated BCCD

Complex permittivity of fully deuterated BCCD was determined at 10 kHz and for the 10 11 −10 13 Hz (near-millimetre and far-infrared) range in the temperature range of 10 - 300 K. No remarkable difference between the phase transition sequence with respect to BCCD was found. Several weak sharp absorption lines (sometimes time dependent) were observed in the lowest temperature ferroelectric phase which brings evidence for the presence of a metastable modulated phase in some part of the sample. From the results of inelastic neutron scattering the low-frequency phonon branches along c were detemined. Like in BCCD, the lowest Δ 3 branch softens near k m ∽ 0.33c obeying the Cochran law.